Please read our
Published Articles

Monitran Technology is Launched ....more info

Eddy Current Probes

How does an eddy current probe work?

• When an AC current flows in a coil in close proximity to a conducting material the magnetic field of the coil will induce circulating (eddy) currents in the material
• The magnitude and phase of the eddy currents will affect the loading on the coil and hence its impedance.
• Note that to be detected cracks must interrupt the surface eddy current flow
• Cracks lying parallel to the current path will not cause any significant interruption and may not therefore be detected

Cracks in a material are one example of a factor that can affect the magnitude of eddy currents and which are therefore detectable by this method. Other factors include: 

• Conductivity
• Magnetic permeability
• Geometry – e.g. curvature, thickness, edge effects
• Proximity – sensitivity decreases with distance between material and probe and the ‘lift off’ signal also changes
• Depth of penetration
• Characteristic impedance planes for different materials 

 Go back to the FAQ menu